Rubber compositions for tire innerliners or innertubes frequently comprise butyl rubber, halogenated butyl rubber, or both. These rubbers reduce air permeability (i.e., provide good air retention) and provide good durability to the tire innerliner or innertube. However, butyl rubbers and halogenated butyl rubbers can be very expensive. Therefore, tire manufacturers strive to balance the expense of the rubber composition with the performance of the innerliner or innertube.